1. Technical Field of the Invention
The present invention relates to a blade row of an axial flow type compressor in which a rotor blade row and a stator blade row are alternately arranged in an axial direction.
2. Description of the Related Art
In a gas turbine or a jet engine, a compressor for compressing an air introduced from the outside is configured as an axial flow type compressor in which a rotor blade row and a stator blade row are arranged in an axial direction.
In the axial flow type compressor, since an inflow mach number becomes high at a position on the side of a radial inner diameter (on the hub side) of a stator blade forming the stator blade row under the condition of a high flow rate and a high pressure, choking easily occurs in a minimum valid passageway sectional portion (throat area), thereby increasing pressure loss. Additionally, the flow rate cannot increase any more when the choking occurs.
In the axial flow type compressor, a chord length may be increased in order to realize a high pressure at a position on the side of the radial inner diameter (on the hub side) of a rotor blade forming the rotor blade row. However, since friction loss also increases, the advantage of the increased chord length becomes small. Since a relative inflow mach number is large at a position on the side of a radial outer diameter (on the tip side), pressure loss increases due to an acceleration before a throat area. Additionally, since the choking easily occurs, the flow rate cannot increase.
Therefore, Patent Document 1 has already disclosed a technique for solving the above-described problems.
A blade row structure of an axial flow type compressor disclosed in Patent Document 1 aims to realize high flow rate and high efficiency of the compressor. As shown in FIG. 1, in a blade row structure of an axial flow type compressor 65 in which plural blades 63 are arranged between an outer passageway wall 61 and an inner passageway wall 62 arranged in an annular shape so as to have an interval therebetween in a circumferential direction, the inner passageway wall 62 is provided with a concave portion 65 which is located at a throat portion 64, in which a passageway sectional area in the row of the blades 63 becomes minimum, so as to expand a passageway sectional area, and is provided with a smooth convex portion 68 which is located on the downstream side of the concave portion 65 so as to suppress a deceleration of a fluid flowing through a base portion 67 on the rear side of the blade.
Additionally, Patent Documents 2 and 3 have disclosed a centrifugal compressor different from the axial flow type compressor.
In Patent Document 2, as shown in FIG. 2, there is disclosed an impeller including a hub 71, plural main blades 72 which are formed in the hub, and plural splitter blades 73 which are formed in the hub. In this impeller, each splitter blade 73 is formed between the adjacent main blades 72.
In Patent Document 3, as shown in FIG. 3, there is disclosed an impeller including a rotary disc 82 which has a hub 81 suitable for a rotary shaft, plural full blades 83 which are formed on a surface of the rotary disc, and plural splitter blades 84 which are formed on the surface of the rotary disc. In this impeller, the full blades 83 and the splitter blades 84 are alternately arranged in a rotary direction of the rotary disc.
[Patent Document 1]
Japanese Patent Application Laid-Open No. H06-257597 “BLADE ROW STRUCTURE OF AXIAL FLOW TYPE COMPRESSOR”
[Patent Document 2]
U.S. Pat. No. 5,002,461
[Patent Document 3]
U.S. Pat. No. 5,639,217
As described above, in the axial flow type compressor, a problem arises in that pressure loss of the rotor blade row and the stator blade row increases in the case of a high inflow mach number, and a problem arises in that a choking occurs in the throat portion in the blade row and an inflow air flow rate is limited. In Patent Document 1 described above, it is expected that a local advantage is exhibited, but a three-dimensional advantage is small.
Additionally, especially in the case of a fan, it is configured such that the number of the stator blades is larger than that of the rotor blades and a cutoff condition advantageous in noise is established. However, as described above, in order to handle the high-mach-number fluid, it is necessary to expand an area between blades. As expanding means, means for decreasing the number of stator blades may be supposed. However, since the number of rotor blades is approximately equal to that of the stator blades, a problem arises in that noise increases.